JP6208338B2 - Method and apparatus for generating expanded microspheres - Google Patents

Description

  The present invention relates to expanded thermoplastic microspheres and methods for making devices therefor.

  Thermally expandable microspheres are known in the art and are described in detail, for example, in US Pat. No. 3,615,972. Various grades of expandable microspheres with different expansion temperatures are commercially available from AkzoNobel as either a dry, free-flowing microsphere or as an aqueous slurry of microspheres under the trademark Expancel ™ .

  Such expandable microspheres include a foaming agent encapsulated in a thermoplastic shell. When heated, the foaming agent evaporates and the internal pressure increases and at the same time the shell softens, resulting in significant expansion of the microspheres, usually 2 to 5 times the diameter.

  Thermoplastic microspheres can be used in a variety of applications, unexpanded or pre-expanded. Examples of products in which (essentially anhydrous) dry-expanded microspheres are used are as sensitizers for emulsion explosives and a variety of organic solvent-based paints, as well as artificial marble, polyester putty, and artificial wood The use as a lightweight filler of a thermosetting material is mentioned. In many products such as water-soluble paints, thermal paper, porous ceramics, and emulsion explosives, wet expanded microspheres are usually used as aqueous slurries.

  Substantial space is required for transportation of the already expanded microspheres. For this reason, unexpanded microspheres are often transported to the end user in place of the expanded microspheres, and they are expanded on site. The microspheres can then be expanded directly, for example, just before or during the process of producing any of the end products described above.

  Various methods and devices have been developed to expand thermoplastic microspheres.

  U.S. Pat. No. 5,484,815 and U.S. Pat. No. 7,192,989 disclose methods and apparatus suitable for expanding dry microspheres.

  In U.S. Pat. No. 4,513,106, the microspheres are heated and at least partially expanded by introducing a sufficient amount of steam into the slurry in the pressure zone to partially expand the microspheres. By allowing the microspheres to exit the pressure zone in a reduced pressure condition, further expanding the microspheres and accelerating to a flow at a speed of at least 1 m / s, expanding the microspheres in an aqueous slurry Discloses a method and apparatus suitable for use in

  The advantage of expanding the microspheres in the aqueous slurry is that dusting is avoided. However, it is desirable to further improve existing techniques for expanding microspheres within a slurry.

  It is an object of the present invention to provide a method and apparatus for expanding microspheres in a slurry without introducing extra moisture.

  Another object of the present invention is to provide a method and apparatus for expanding microspheres in a slurry that is flexible with respect to the liquid used in the slurry.

  Yet another object of the present invention is to provide a method and apparatus for expanding microspheres in a slurry that is flexible with respect to the means for heating the microspheres.

  Yet another object of the present invention is to provide a method and apparatus for expanding microspheres in a slurry that has a low risk of microsphere aggregation.

  Yet another object of the present invention is to provide a method and apparatus for expanding microspheres in a slurry that can be used for a wide range of microsphere grades having various expansion temperatures.

  It has been found that these and other objects can be achieved in accordance with the present invention by the methods and apparatus according to the appended claims.

It is a figure which shows embodiment of this invention.

More particularly, the present invention relates to a method for producing expanded thermoplastic microspheres from unexpanded thermally expandable thermoplastic microspheres comprising a thermoplastic polymer shell encapsulating a blowing agent, said method comprising:
(A) supplying a slurry of such expandable thermoplastic microspheres in a liquid medium to a heating zone;
(B) heating the slurry in the heating zone without direct contact with any fluid heat transfer medium such that the expandable thermoplastic microspheres reach a temperature at which expansion begins at least at atmospheric pressure; and Maintaining a sufficient pressure in the heating zone so that the microspheres in the slurry do not fully expand, and (c) withdrawing the slurry of the expandable microspheres from the heating zone Extracting the slurry into a zone where the pressure is sufficiently low so that the microspheres expand.

  The invention further relates to a device for expanding an unexpanded thermally expandable thermoplastic microsphere comprising a thermoplastic polymer shell encapsulating a foaming agent, said device having an outlet and an inlet and at a pressure of at least 4 bar. Any heat transfer medium capable of withstanding a heating zone, means for supplying a slurry of unexpanded thermally expandable thermoplastic microspheres in a liquid medium to the heating zone and generating a pressure of at least 4 bar in the heating zone; And means for heating the slurry of the expandable microspheres to a temperature of at least 60 ° C. without direct contact therewith.

  Unexpanded, thermally expandable thermoplastic microspheres are hereinafter referred to as expandable microspheres. The particle size of the expandable microspheres can vary within wide limits and can be selected for the desired properties of the product in which they are used. In most cases, the preferred volume median diameter is 1 μm to 1 mm, preferably 2 μm to 0.5 mm, especially 3 μm to 100 μm, as measured by scattering of laser light on a wet sample on a Malvern Mastersizer Hydro2000SM instrument. is there. The diameter of the microsphere increases, for example, by 2 to 5 times during expansion.

  The liquid medium of the expandable microsphere slurry may be any liquid that is inert to the microspheres and can withstand the temperature at which the slurry is heated. In many cases, water or an aqueous liquid is preferred, thus forming an aqueous slurry, but depending on the intended use of the expandable microsphere, an organic liquid such as at least one of vegetable oil, mineral oil, and glycerol may be used for the slurry. May also be preferred, and these organic liquids may be anhydrous. Because the method of the present invention does not require steam or any other form of water to be added to the slurry, it is possible to produce a slurry of anhydrous expandable microspheres that can be used directly in applications where water is not desired. it can. Furthermore, since no other liquid medium needs to be added to the slurry, it is possible to produce a slurry of expandable microspheres with a high content and controlled solids content.

  In most commercial methods of producing expandable microspheres, usually obtained first as an aqueous slurry, such slurry is optionally diluted or dehydrated to the desired microsphere content and then the method of the present invention. Can be used directly. On the other hand, such aqueous slurries may be dried to obtain essentially anhydrous microspheres that can be used to produce slurries of organic liquids.

  The content of expandable microspheres in the slurry depends on what is required of the product obtained after expansion. The upper limit is limited by the pumping capacity of the slurry and by the transportability of the slurry through the heating zone. In most cases, the content of expandable microspheres is suitably 5 to 50 wt%, preferably 10 to 40 wt%, and most preferably 15 to 30 wt%.

  The slurry of expandable microspheres flows through a heating zone that can be made of any vessel, pipe, or tube that is provided with an outlet and an inlet and withstands the pressure maintained therein. The means for heating the slurry therein may be, for example, a fluid heat transfer medium that is not in direct contact with the slurry, an electrical heating element, or a microwave. For example, the heating zone may be a heat exchanger comprising at least one pipe or tube surrounded by a heat transfer medium that is not in direct contact with the expandable microsphere slurry. The heat exchanger is, for example, 2-10 pipes or tubes, preferably several parallel pipes or tubes, preferably connected to a common inlet and a common outlet. A tube may be provided. It is also possible to have only one pipe or tube. The advantage of using a single (ie only one) pipe or tube is to reduce the risk of non-uniform flow distribution caused by partial clogging of one of several parallel pipes Accompanied by. Such a single pipe or tube is preferably surrounded by a heat transfer medium such as hot water, which is preferably arranged in a container or tank containing the heat transfer medium.

  The heat transfer medium may be any suitable fluid medium such as hot water, steam or oil. Alternatively, heat may be supplied by an electrical heating element, for example, inside or outside the heating zone, on the wall surface, or any combination thereof. As yet another method, heat may be supplied by electromagnetic radiation such as microwaves.

  Through the present invention, it is possible to extend the grade of microspheres that require higher temperatures than can almost be achieved with steam, for example by using an electrical heating element or hot oil as the heat transfer medium. For example, it is possible to expand microspheres that require temperatures above 200 ° C. Also, for example, by using a heat transfer medium having a relatively low temperature of 60-100 ° C., such as hot water, to expand the microspheres that may collapse or otherwise be damaged if the temperature is too high. Is also possible.

  A vessel or at least one pipe or tube through which a slurry of expandable microspheres flows, especially if the heating of the slurry is provided by a fluid heat transfer medium or by an electrical heating element, such as a heat conductive material such as steel or copper It is preferable that Where heating is provided by electromagnetic radiation, the container or at least one pipe or tube is preferably a material, such as various polymeric materials, that transmits such radiation.

  In a heat exchanger comprising at least one pipe or tube, such at least one pipe or tube preferably has an inner diameter of 2 to 25 mm or more and an inner diameter of 4 to 15 mm, respectively, or Most preferably, it is 6-12 mm. The thickness of the wall of at least one pipe or tube is suitably 0.5 to 3 mm, preferably 0.7 to 1.5 mm.

  Where heating is performed by an electrical heating element, such a heating element may be provided, for example, inside and / or outside of at least one pipe or tube, for example a single pipe or tube. Such pipes or tubes have an inner diameter of, for example, 20-80 mm, or 35-65 mm. For example, the heating element can be provided in the center of the interior of the pipe or tube, and the slurry of expandable microspheres flows through the gap around the heating element. Such an electrical heating element may itself be a pipe or tube having a main electrical heating source therein, and heat is transferred through the walls to the slurry flowing through the gap. The electric heating element is preferably provided both inside and outside the at least one pipe or tube.

  The optimum size and volume of the means for heating the slurry is determined by the slurry flow rate, slurry concentration, and incoming slurry temperature, and the microspheres expand when the pressure drops after the slurry passes through the heating zone outlet. It must be sufficient to reach the high temperatures necessary to do it. This temperature is always higher than the volatilization temperature of a particular microsphere blowing agent.

  Since the slurry of expandable microspheres is fed through the inlet to the heating zone, preferably by a pump that provides sufficient high pressure to the heating zone, the microspheres do not expand completely therein. The microspheres can be partially expanded within the heating zone, for example, up to 10-80% of the volume after expansion is completed outside the heating zone, or up to 20-70%. It can also be prevented from expanding at all. Examples of suitable pumps include hydraulic diaphragm pumps, piston pumps, screw pumps (eg, eccentric screw pumps), gear pumps, rotary lobe pumps, centrifugal pumps, and the like. A hydraulic diaphragm pump is particularly preferred. The pump preferably also generates a force to transfer the slurry through the heating zone to its outlet. The apparatus may further include a conduit for transporting the expandable microsphere slurry to a pump, for example, from a tank holding the slurry.

  In order to maintain a sufficiently high pressure in the heating zone, the expandable microsphere slurry passes through its outlet, generating a pressure drop corresponding to the pressure difference between the inside of the heating zone and the outside of the heating zone. Extracted from the heating zone. The pressure drop can be generated by any suitable means, such as flow area limitations, such as valves, nozzles or other types of narrow passages. The outlet of the heating zone may be, for example, at its end as required, 0.9 to 0.05 times, or 0.5 to 0.05 times, preferably 0.3 to 0.00 times the inner diameter of the pipe or tube. It may be an insulated pipe or tube, preferably with a flow area limitation such as an opening with a diameter of 1 ×. However, flow area limitations and other special means are not necessarily required and are typically generated at the outlet having the same flow area as the heating zone to prevent the microsphere expansion from completing within the heating zone. A sufficient pressure drop is sufficient. The pipe or tube may be stiff or soft, in the latter case it can be easily guided to the desired exit point of the microsphere without moving the entire device.

  The exact pressure required for the heating zone depends on the temperature and type of the microsphere. The pressure maintained in the heating zone is preferably 4 bar, most preferably at least 10 bar. The upper limit is determined by practical considerations and may be, for example, up to 40 bar or up to 50 bar. The heating zone should therefore preferably be able to withstand such pressures.

  The temperature of the expandable microspheres in the heating zone is usually essentially the same as the temperature of the slurry therein. The exact temperature at which the slurry is heated depends on the grade of the microsphere. For most grades of microspheres, the temperature is preferably in the range of 60-160 ° C, preferably 80-160 degrees, or 100-150 ° C, while for some grades of microspheres, Further, a high temperature such as 250 ° C. or higher may be required. The means for heating the slurry should therefore preferably be able to heat the slurry to such temperatures.

  In the heating zone, a flow of expandable microsphere slurry is transferred from the inlet to the outlet, and under pressure, heated to a high temperature sufficient to cause the microspheres to partially expand therein as needed, And at least at the outlet of the heating zone, it is heated to expand when the pressure drops and enters the zone at a sufficiently low pressure. The zone pressure is usually essentially atmospheric pressure, but may be maintained at a higher or lower pressure depending on the temperature of the microsphere. At this stage, the microspheres are usually also cooled by the ambient air in the zone. The average residence time of the microspheres in the heating zone is preferably long enough to ensure that the slurry reaches a sufficiently high temperature and is maintained for subsequent expansion. In order to ensure high quality and uniform quality production, the apparatus can be further provided with a pulsation damper to stabilize the slurry flow, if desired.

  At the pressure drop at the exit of the heating zone, the microsphere flow also accelerates significantly as expansion proceeds or begins. At the same time, the microspheres are automatically cooled to such a low temperature that expansion stops, forming a point where expansion is complete. In order to optimize the collapse of the microspheres and avoid agglomeration, the pressure drop preferably occurs over as short a distance as possible in the direction of flow.

  Normally, expanded microspheres will not substantially agglomerate because the collapse and cooling of the microspheres after a pressure drop at the exit of the heating zone occurs rapidly. The expanded microspheres can be used immediately for their intended purpose or packed into plastic bags, cartridges or other suitable packages.

  The method and apparatus of the present invention includes, for example, emulsion explosives, paints, polyester putty, polyester, polyurethane or an artificial wood composition based on epoxy, artificial marble based on epoxy, porous ceramics, gypsum board, under In-situ in the manufacture of body coatings, elastomers, crack fillers, sealants, adhesives, phenolic resins, stuccos, cable filling compounds, modeling clays, microcell polyurethane foams, thermal paper coatings, and other types of coatings Particularly useful for expansion. The expanded microsphere stream that activates the device can then be added directly to the production line of such products. For example, the expanded microsphere stream can be added in-line directly into the emulsion flow during the production of the emulsion explosive or directly into the emulsion flow while loading the emulsion explosive from the track into the borehole. it can. In the latter case, the explosive can be sensitized at the mining site and transported unsensitized to the mining site.

  The method and the expansion device according to the invention can be used for all known types of expandable thermoplastic microspheres sold under the trademark Expancel ™. Useful expandable thermoplastic microspheres and their production are described, for example, in US Pat. No. 3,615,972, US Pat. No. 3,945,956, US Pat. No. 4,287,308, US Pat. No. 5,536,756, US Pat. US Pat. No. 6,235,800, US Pat. No. 6,235,394, US Pat. No. 6,509,384, US Pat. No. 6,617,363, and US Pat. No. 6,984,347, US Patent Application Publication No. 2004/0176486, And US Patent Application Publication No. 2005/0079352, European Patent No. 486,080, European Patent No. 567367, European Patent No. 10671151, European Patent No. 1230975, European Patent No. 1288272 Description, European Patent No. 159840 Specification, European Patent No. 1811007, and European Patent Application Publication No. 1964903, International Publication No. 2002/096635 Pamphlet, International Publication No. 2004/072160 Pamphlet, International Publication No. 2007/091960 Pamphlet, It is also described in International Publication No. 2007/091961 pamphlet, International Publication No. 2007/142593 pamphlet, and Japanese Unexamined Patent Publication Nos. 1987-286534 and 2005-272633.

  Suitable thermoplastic microspheres preferably have a thermoplastic shell made of a polymer or copolymer obtained by polymerizing various ethylenically unsaturated monomers, the ethylenically unsaturated monomers being acrylonitrile, methacrylonitrile, Nitrile monomers such as α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, crotononitrile, acrylic esters such as methyl acrylate or ethyl acrylate, methacrylic esters such as methyl methacrylate, isobornyl methacrylate, or ethyl methacrylate, Vinyl halides such as vinyl chloride, vinylidene halides such as vinylidene chloride, vinyl esters such as vinylpyridine and vinyl acetate, styrene such as styrene, halogenated styrene or α-methylstyrene, There are dienes such as butadiene, may be isoprene, and chloroprene. Also, any mixture of the above monomers can be used.

  Monomers for the polymer shell are also divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di ( (Meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,10-decanediol Di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, pentaerythritol hexa (meth) acrylate, dimethylol tricyclodecanedi ( (Meth) acrylate, triallylform tri (meth) acrylate, allyl methacrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane triacrylate, tributanediol di (meth) acrylate, PEG200 di (meth) acrylate One or more of PEG400 di (meth) acrylate, PEG600 di (meth) acrylate, 3-acrylyloxyglycol monoacrylate, triacryl formal or triallyl isocyanate, triallyl isocyanurate, etc. It may be desirable to include a crosslinked polyfunctional monomer. When present, such cross-linking monomers preferably comprise a total amount of 0.1 to 1 wt%, most preferably 0.2 to 0.5 wt% of monomer, based on the polymer shell. The polymer shell preferably consists of 60-95 wt% of the total microspheres, most preferably 75-85 wt%.

Usually, the softening temperature of the polymer shell corresponding to the glass transition temperature (T _g ) is preferably in the range of 50 to 250 ° C. or 100 to 230 ° C.

  The blowing agent within the microsphere is usually a liquid having a boiling temperature not higher than the softening temperature of the thermoplastic polymer shell. Blowing agents, sometimes called foaming agents or propellants, are n-pentane, isopentane, neopentane, butane, isobutane, hexane, isohexane, neohexane, heptane, isoheptane, octane, and isooctane, or mixtures thereof, It may be at least one hydrocarbon. Also, petroleum ether and other hydrocarbon materials such as chlorinated or fluorinated hydrocarbons such as methyl chloride, methylene chloride, dichloroethane, dichloroethylene, trichloroethane, trichloroethylene, trichlorofluoromethane, and the like can be used. Particularly preferred blowing agents include at least one of isobutane, isopentane, isohexane, cyclohexane, isooctane, isododecane, and mixtures thereof, and preferably contain isooctane. Suitably the blowing agent is made from 5 to 40% by weight of the microspheres.

  The boiling point of the blowing agent at atmospheric pressure may be within a wide range, preferably −20 to 200 ° C., most preferably −20 to 150 ° C., and most preferably −20 to 100 ° C.

The temperature at which the expandable microsphere begins to expand depends on the combination of the blowing agent and the polymer shell, and microspheres having various expansion temperatures are commercially available. The temperature at which the expandable microsphere begins to expand at atmospheric pressure is called _Tstart . Expandable microspheres used in the present invention preferably has a T _start of 40-230 ° C., most preferably 60 to 180 ° C..

  The accompanying drawings illustrate embodiments of the present invention.

  The drawing shows a device comprising a hydraulic diaphragm pump 1 connected to a heat exchanger 4 (forming a heating zone) and a pulsation damper 2. The heat exchanger 4 is provided with an inlet 10 and an outlet 8 in the form of a pipe, and in the shape of a nozzle, the flow region is restricted at the end. The heat exchanger further includes one or more tubes (not shown) surrounded by a heat transfer medium (not shown) such as hot water, steam or oil. The apparatus further includes a pressure gauge 3, a safety valve 5, a control valve 6, a thermometer 7, and a three-way valve 9.

  The apparatus operates by, for example, feeding a slurry of expandable microspheres from a slurry tank (not shown) by a hydraulic diaphragm pump 1 through a heat exchanger 4, and in the heat exchanger 4, the slurry is With the heat transfer medium, the microspheres are heated to a temperature at which they start to expand or at least start to expand at atmospheric pressure. The hydraulic diaphragm pump transfers the slurry through the heat exchanger 4 and generates enough pressure to prevent the microspheres from fully expanding therein. The thermal slurry flows out through the outlet 8 and looks like outside, and if necessary, the flow area is restricted to create a pressure drop to atmospheric pressure, so that the microspheres expand rapidly in the outside air. Then cooled. The pulsation damper 2 suppresses the fluctuation of the slurry flow from the hydraulic diaphragm pump 1. The pressure and temperature in the heat exchanger can be monitored by the pressure gauge 3 and the thermometer 7, respectively. This device can be cleaned by replacing the slurry of expandable microspheres with, for example, cleaning water, using a three-way valve 9 in front of the pump 1. The flow and pressure of the heat transfer medium used in the heat exchanger 4 are adjusted by the control valve 6.

Example 1:
AkzoNobel's expandable microsphere Expancel ™ 051-40 was expanded using an apparatus according to the accompanying drawings. An aqueous slurry of 15 wt% microspheres at a temperature of 20 ° C. is provided with seven tubes each surrounded by thermal steam as a heat transfer medium, each having an inner diameter of 10 mm, an outer diameter of 12 mm, and a length of 1.95 meters. It was fed through a heat exchanger at a rate of 3 liters / minute. The pump produced a pressure of 30 bar maintained in the heat exchanger and the steam transferred enough thermal energy to heat the slurry to 130 ° C. The microspheres exited the heat exchanger through a nozzle-equipped outlet with a 1.5 mm opening and entered the outside air at 20 ° C. and expanded until a density of 22 g / dm ³ was reached. The expanded microsphere product had a solid content of 15 wt% and microscopic examination showed that this product had no agglomeration.

Example 2:
AkzoNobel's expandable microsphere Expancel (TM) 031 is used in a device equipped with a single copper tube of 5.8 m length, located in a tank filled with hot water maintained at a temperature of 100 ° C. And inflated. The copper tube had an inner diameter of 6.3 mm and an outer diameter of 7.8 mm, but had no flow area limitations. An aqueous slurry of 20 wt% microspheres at a temperature of 20 ° C. was pumped by a diaphragm pump at a rate of 80 liters / hour through a copper tube surrounded by hot water as a heat transfer medium. The diaphragm pump produced a pressure of 6 bar. The microspheres exited the copper tube heat exchanger through the outlet and reached a density of 24 g / dm ³ after final expansion. The expanded microsphere product had a solids content of 20 wt% and microscopic examination showed that the product was essentially free of agglomeration.
Note that the present invention includes the following aspects.
[1]
A method for producing an expanded thermoplastic microsphere from an unexpanded thermally expandable thermoplastic microsphere comprising a thermoplastic polymer shell encapsulating a blowing agent, comprising:
(A) supplying a slurry of such expandable thermoplastic microspheres in a liquid medium to a heating zone;
(B) heating the slurry in the heating zone without direct contact with any fluid heat transfer medium such that the expandable thermoplastic microspheres reach a temperature at which expansion begins at least at atmospheric pressure; and Maintaining the pressure sufficiently high in the heating zone so that the microspheres in the slurry do not fully expand; and
(C) extracting the slurry of the expandable microspheres from the heating zone and into a zone where the pressure is sufficiently low so that the microspheres expand.
Including said method.
[2]
The method according to [1], wherein the pressure in the heating zone is maintained at 5-50 bar.
[3]
The method according to any one of [1] to [2], wherein the slurry of the expandable microsphere is heated to a temperature of 60 to 160 ° C. in the heating zone.
[4]
Heat exchange comprising the slurry of the expandable microsphere flowing through a heating zone, the heating zone comprising at least one pipe or tube surrounded by a heat transfer medium that is not in direct contact with the slurry of the expandable microsphere The method according to any one of [1] to [3], which is a container.
[5]
The method according to [4], wherein each of the at least one pipe or tube has an inner diameter of 2 to 25 mm.
[6]
The method according to any one of [1] to [3], wherein the heat is supplied by an electric heating element.
[7]
The slurry of the expandable microspheres is withdrawn from the heating zone through the heating zone outlet, the outlet corresponding to a pressure difference between the inside of the heating zone and the outside of the heating zone. The method according to any one of [1] to [6], wherein a pressure drop is generated.
[8]
The method according to [7], wherein the outlet is provided with a flow region restriction for generating the pressure drop.
[9]
The method according to any one of [1] to [8], wherein the slurry of the expandable microsphere is extracted from the heating zone and enters an atmospheric pressure zone.
[10]
Any of [1] to [9], wherein the slurry of the expandable microsphere is supplied to the heating zone by a pump that provides a sufficiently high pressure to the heating zone so that the microsphere does not expand completely. The method described in 1.
[11]
An apparatus for expanding an unexpanded, thermally expandable thermoplastic microsphere, comprising a thermoplastic polymer shell encapsulating a blowing agent,
A heating zone having an outlet and an inlet and capable of withstanding a pressure of at least 4 bar;
Means for supplying a slurry of the unexpanded thermally expandable thermoplastic microspheres in a liquid medium to the heating zone, the means capable of generating a pressure of at least 4 bar in the heating zone;
Means for heating the slurry of the expandable microspheres to a temperature of at least 60 ° C. without direct contact with any fluid heat transfer medium;
Said device.
[12]
[11], wherein the outlet is provided with a flow region restriction sufficient to generate a pressure drop corresponding to a pressure difference between the inside of the heating zone and the outside of the heating zone. apparatus.
[13]
Any of [11] to [12], wherein the heating zone is a heat exchanger including at least one pipe or tube surrounded by a heat transfer medium that does not directly contact the slurry of the expandable microsphere. The device described.
[14]
The apparatus according to any of [11] to [13], wherein the heating zone comprises a single pipe or tube surrounded by a heat transfer medium that is not in direct contact with the slurry of the expandable microsphere.
[15]
[11] to [12], wherein the heating zone includes at least one pipe or tube and an electric heating element provided inside and / or outside the at least one pipe or tube. The device described.

Claims (15)

A method for producing an expanded thermoplastic microsphere from an unexpanded thermally expandable thermoplastic microsphere comprising a thermoplastic polymer shell encapsulating a blowing agent, comprising:
(A) supplying a slurry of the unexpanded thermally expandable thermoplastic microspheres in a liquid medium to a heating zone;
(B) the unexpanded thermally expandable thermoplastic microsphere slurry is in any fluid heat transfer medium so that the unexpanded thermally expandable thermoplastic microspheres reach a temperature at which expansion begins at least at atmospheric pressure. Heating the unexpanded thermally expandable thermoplastic microsphere slurry in the heating zone without direct contact, and in the heating zone so that the microspheres in the slurry do not fully expand. maintaining a pressure high enough, and the (c) the slurry of the expandable microspheres is extracted from the heating zone, wherein the microspheres are Ru put into a sufficiently low zone pressure to expand It said method comprising a call.   The method of claim 1, wherein the pressure in the heating zone is maintained at 5-50 bar.   The method according to claim 1, wherein the slurry of the expandable microsphere is heated to a temperature of 60 to 160 ° C. in the heating zone.   Heat exchange comprising the slurry of the expandable microsphere flowing through a heating zone, the heating zone comprising at least one pipe or tube surrounded by a heat transfer medium that is not in direct contact with the slurry of the expandable microsphere 4. The method according to any one of claims 1 to 3, wherein the method is a vessel.   The method of claim 4, wherein the at least one pipe or tube each has an inner diameter of 2 to 25 mm.   The method according to any one of claims 1 to 3, wherein the heat is supplied by an electric heating element.   The slurry of the expandable microspheres is withdrawn from the heating zone through the heating zone outlet, the outlet corresponding to a pressure difference between the inside of the heating zone and the outside of the heating zone. The method according to claim 1, wherein a pressure drop is generated.   The method of claim 7, wherein the outlet is provided with a flow region restriction for generating the pressure drop.   9. A method according to any one of the preceding claims, wherein the slurry of expandable microspheres is withdrawn from the heating zone and enters an atmospheric pressure zone.   The slurry of the expandable microsphere is supplied to the heating zone by a pump that provides a sufficiently high pressure to the heating zone so that the microsphere does not expand completely. The method described in 1. An apparatus for expanding an unexpanded, thermally expandable thermoplastic microsphere, comprising a thermoplastic polymer shell encapsulating a blowing agent,
A heating zone having an outlet and an inlet and capable of withstanding a pressure of at least 4 bar;
Means for supplying a slurry of the unexpanded thermally expandable thermoplastic microspheres in a liquid medium to the heating zone, the means capable of generating a pressure of at least 4 bar in the heating zone;
Means for heating the slurry of the expandable microspheres to a temperature of at least 60 ° C. without direct contact with any fluid heat transfer medium.   12. The flow area restriction of claim 11, wherein the outlet is provided with a flow region restriction sufficient to generate a pressure drop corresponding to a pressure difference between the interior of the heating zone and the exterior of the heating zone. apparatus.   13. The heat exchanger according to claim 11, wherein the heating zone is a heat exchanger comprising at least one pipe or tube surrounded by a heat transfer medium that is not in direct contact with the slurry of the expandable microsphere. The device described.   14. Apparatus according to any one of claims 11 to 13, wherein the heating zone comprises a single pipe or tube surrounded by a heat transfer medium that is not in direct contact with the slurry of the expandable microspheres. The heating zone comprises at least one pipe or tube and an electric heating element provided inside and / or outside the at least one pipe or tube. The device described.